APS_April 2023

J ournal of the A merican P omological S ociety

106

290 Figure 2. Seasonal yield for grafted and own-rooted ‘Patrecia’ SHB grown in a minimally 291 amended field in Citra, FL. Control = own-rooted ‘Patrecia’. R1, R2, R3 = ‘Patrecia’ grafted on 292 Rootstock 1, Rootstock 2, or Rootstock 3, respectively. Boxes topped by the same letter were 293 not significantly different according to the least significant difference test at P < 0.05, by LSD. 294 Range of Y axis (Total yield) is different for each graph. Figure 2. Seasonal yield for grafted and own-rooted ‘Patrecia’ SHB grown in a minimally amended field in Citra, FL. Control = own-rooted ‘Patrecia’. R1, R2, R3 = ‘Patrecia’ grafted on Rootstock 1, Rootstock 2, or Rootstock 3, respectively. Boxes topped by the same letter were not significantly different according to the least significant difference test at P < 0.05, by LSD. Range of Y axis (Total yield) is different for each graph.

Results and Discussion Yield. In this experiment, total yield and average berry weight were low and not dif ferent among treatments during the 2019 season (Fig. 2). Low yields during the 2019 season were likely due to the long establish ment period blueberry plants typically have in a production field. Casamali et al. (2016a) found that in the first fruiting season after grafting, yields of grafted plants were lower than yields of own-rooted plants. The clonal rootstocks evaluated in this trial followed the same trend. Yields increased substantially in 2021 and 2022 (Fig. 2) and yields of plants grafted onto R1 and R2 were significantly higher than the own-rooted controls in both seasons. Yields of plants grafted onto R3 were higher than the control only in 2021. Results from R1 and R2 agree with previ ous findings where grafted plants exhibited higher yields than own-rooted plants in soils considered suboptimal for blueberry (Darnell et al., 2020). However, rootstock R3 did not always follow this trend, suggesting further work is necessary to identify optimum scion rootstock combinations. Considering grafted plants were equally or more productive than own-rooted plants in minimally amended soils, it is possible that grafting reduces the need for pine bark and sulfur during estab

lishment and cultivation. This reduction may lower establishment and production cost for blueberry production. Economic analysis is necessary to establish if using more costly plant material (grafted plants) while reducing establishment and production costs can make blueberry production more economically sustainable. Longer-term testing of grafted blueberry production is also necessary to es tablish if eventual addition of organic matter and acidifying agents is necessary. Berry weight. In 2019 and 2021, average berry weight was not affected by the treat ments (Fig. 3). In 2019, fruits in all treat ments had lower berry weights than the 3 g average for the cultivar ‘Patrecia’ (Munoz, 2016) (avg = 1.95 g), likely due to plant age as detailed above. In 2021, the average berry weight achieved the 3 g standard for ‘Patrecia’. In 2022, the average berry weight was similar to 2021, but own-rooted plants had significantly lower average berry weight than grafted plants. Casamali et al. (2016a) also reported greater mean berry weight from SHB grafted on sparkleberry seedlings ver sus same age own-rooted SHB. Firmness. Berry firmness was not affected by the treatments in early or late season in 2021 or early season in 2022 (Table 1). How ever, in 2022, late season fruit from grafted

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